The overall objective of the proposed research is to code existing serial 12-lead electrocardiographic (EGG) tracings in order to: 1) assess the incidence of ECG abnormalities in young adults of different races;2) examine potential risk factors for development and progression of ECG abnormalities;3) investigate associations between ECG abnormalities and other measures of subclinical cardiac disease (subclinical atherosclerosis, left ventricular mass/hypertrophy, and autonomic dysfunction);and 4) assess differences in incidence and patterns of associations of ECG abnormalities in blacks and whites. Ultimately, the results of the study may help to define a potential role for the resting ECG (a low-cost, non-invasive, widely available and easily interpretable clinical test) in primary prevention of CVD. We will perform this study in the large biracial cohort of men and women participants of the Coronary Artery Risk Development in Young Adults (CARDIA) Study, who were aged 18 to 30 years at enrollment in 1985-1986. We plan to code resting 12-lead ECGs obtained from CARDIA participants at the Year 0, Year 7, and Year 20 examinations, using state-of- the-art technology and standardized Minnesota Code and Novacode methods. This project will provide the first analyses of long-term ECG changes in young black and white adults, during a critical age period when these abnormalities appear to develop. The proposed study is unique, timely and extremely cost-effective in that it takes advantage of a large, pre-existing, biracial epidemiologic cohort study with high-quality serial 12- lead ECG tracings (previously collected but never coded) and with other previously collected measures of CVD risk factors, subclinical atherosclerosis and left ventricular morphology. It is unlikely that other cohort studies will be able to provide similar data for the foreseeable future. The resting 12-lead ECGs from CARDIA represent a precious resource for research that can offer important insights into the epidemiologic associations between ECG abnormalities and CVD. The proposed research will fill critical gaps in our knowledge of the epidemiology, etiology and natural history of ECG abnormalities in young adults. Furthermore, it will provide important insights into the potential mechanisms by which ECG abnormalities are associated with increased risk for CVD, and how these mechanisms may differ between blacks and whites, which may ultimately lead to improvements in preventive strategies for young adults.